Modeling Analysis of Biogenic Secondary Organic Aerosol Dependence on Anthropogenic Emissions in China

Abstract

Biogenic secondary organic aerosol (BSOA) produced from naturally emitted biogenic volatile organic compounds (BVOCs) is closely affected by anthropogenic emissions. Reactive nitrogen oxides (NOx), sulfate (SO4), and primary organic aerosol (POA) modulate transformations of BVOCs by altering the oxidation pathways and gas–particle partitioning processes. China has experienced rapid changes in anthropogenic emissions recently, but the response of BSOA remains unclear. We conducted GEOS-Chem simulations to examine this response and found that isoprene-derived SOA increased (3.1%/yr) similarly as SO4 (3.6%/yr) over 2000–2006 but declined faster (−8.0%/yr) than SO4 (−4.3%/yr) over 2007–2015. Sensitivity simulations suggested that SO4 significantly promoted heterogeneous reactive uptake of isoprene epoxydiols (IEPOX) formed SOA (SOAIE), and a high level of NOx suppressed the production of IEPOX and subsequently reduced SOAIE. The model roughly reproduced observed declines of secondary organic carbon (SOC) and SO4 at a rural site in South China over 2007–2011, although the mass concentrations were substantially underestimated. We find that BSOA would contribute slightly more to PM2.5 (2.8%) in 2050 under the RCP4.5 scenario than the present day (2.1%). This model-based work provides insights into historical and future changes of BSOA and implies the need to consider the controllable part for air quality management.